Multiple myeloma (also known as MM, myeloma, plasma cell myeloma, or Kahler's disease) is a type of cancer of plasma cells, which are antibody-producing immune system cells. Symptoms of multiple myeloma include bone pain, infection, renal failure, anemia, and bone lesions. The disease is considered incurable, and only a few treatments, such as lenalidomide (REVLIMID®) are available and show promise. As such, a need exists for new treatments for multiple myeloma. To date, no one has described the ability of non-hematopoietic, tissue culture plastic-adherent placental stem cells to suppress the growth of bone-related cancers, e.g., multiple myeloma, or to suppress the proliferation of cells of bone-related cancers.